Mechanism of polymer adsorption on shale surfaces: Effect of polymer type and presence of monovalent and divalent salts

Abstract

This paper studies the adsorption behavior of representative guar-based polymers onto the surface of source rock outcrop samples to provide a better picture of the interaction(s) of polymers with these rocks. Outcrop samples from the Barnett, Eagle Ford, and Marcellus shales were collected, analyzed for mineralogy and total organic content, and then exposed to different polymer solutions under elevated temperature and moderately elevated pressure. Viscosities of these polymer solutions were measured before and after exposure to the rock samples to establish a correlation between polymer adsorption and rock mineralogy and/or organic content. Results indicate a direct correlation between polymer adsorption and both rock mineralogy. Cationic polymers are shown to be more prone to adsorption onto the surface of the rock than non-ionic polymers. The results from this work establish that fluid-rock interactions are significant and that further research regarding shale polymer interactions and its effects on hydrocarbon production is needed with representative downhole shale samples given the trends now shown with outcrop samples.